Soap-Making Manual: A Practical Handbook on the Raw Materials, Their Manipulation, Analysis and Control in the Modern Soap Plant.Thomssen, Edgar George
Science
Soap-Making Manual: A Practical Handbook on the Raw Materials, Their Manipulation, Analysis and Control in the Modern Soap Plant.
Thomssen, Edgar George
Soap
IODINE NUMBER, TUNG OIL--The committee has made an extensive study of
the application of the Wijs method to the determination of iodine value
in the case of tung oil with the result that it recommends the method
for this oil but has thought it desirable to limit the conditions under
which the determination is conducted rather narrowly, although
reasonably good results are obtained by the committee method without
making use of the special limitations.
The co-operative work of the committee and the special investigations
conducted by individual members bring out the following points:
_Influence of Temperature_--From 16deg. C. to 30deg. C. there is a
moderate increase in the absorption, but above 30deg. the increase is
rather rapid so that it was thought best to limit the temperature in the
case of tung oil to 20deg. to 25deg. C.
_Influence of Time_--The absorption increases with the time but
apparently complete absorption, so far as unsaturated bonds are
concerned, occurs well within one hour's time. Consequently, one hour
was set as the practical limit.
_Influence of Excess_--The excess of iodine solution also tends to
increase the iodine number, hence the Committee thought it necessary to
limit the excess rather rigidly to 55 +- 3 per cent, although with
greater latitude results were reasonably good.
_Influence of Age of Solution_--Old solutions tend to give low results
although up to 2 mo. no great differences were observed. Nevertheless,
it was thought best to limit the age of the solution to 30 days--long
enough for all practical purposes.
_Amount of Sample_--As a practical amount of sample to be weighed out
the Committee decided on 0.15 g. with a tolerance of 0.05 g. in either
direction according to preference. In other words, the amount of sample
to be taken for the determination to be from 0.1 to 0.2 g. in the
discretion of the analyst.
The Committee's study of the Huebl method which has been adopted by the
Society for Testing Materials in the case of tung oil indicates that
this method when applied to tung oil is subject to the same influences
as the Wijs method and it has the additional very serious disadvantage
of requiring a long period of time for absorption which cannot be
considered reasonable for a modern analytical method. When using the
Huebl solution, the absorption is not complete in the case of tung oil at
3, 7, 18 or even 24 hrs.
The Hanus method in the case of tung oil gives very high and erratic
results, as high as 180 to 240 in ordinary cases for an oil whose true
iodine number is about 165.
MELTING POINT.
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